1. Field of the Invention
The invention relates to macular degeneration of the eye, and specifically to optical correction techniques that will assist people with macular degeneration to see more clearly.
2. Description of the Related Art
FIG. 1 illustrates a cutaway view of the eye.
Eye 100 is illustrated, with various parts of the eye 100 shown. Those parts that are most familiar to people are the iris 102, pupil 104, lens 106, cornea 108, and retina 110. The iris 102, the “colored” portion of the eye 100, contracts and expands within an opening of the sclera 112 (the “white” part of the eye 100) to change the size of pupil 104, such that light entering the eye 100 through the cornea 108 and lens 106 passes through the vitreous portion 114 and strikes the retina 110. The choroid 116, which lies between the retina 110 and sclera 112, provides the vascular layer and connective tissue between the retina 110 and sclera 112, and as the retina 110 is stimulated by incoming light transmits information from retina 110 to the brain.
The part of the retina 110 that is responsible for central, i.e. “sharp” vision is the macula 120. The macula is a small, oval shaped spot on the back of the retina 110, and is typically about 2.5 to 3 mm in diameter. Near its center is the fovea (not shown), which contains a high concentration of cone cells. Cone cells in the macula 120 detect light and retransmit it as nerve impulses to the brain via the optic nerve 118. The cone cells in the portion of the retina 110 surrounding the fovea and macula 120 are less dense, and are responsible for the so-called peripheral, blurred vision of eye 100.
The health of the eye 100 depends on many factors, and various conditions affect different portions of the eye 100 described above. One condition which is becoming more common is age-related macular degeneration (MD), which is a chronic eye condition that typically affects people age 50 and older, and is the leading cause of severe vision loss in those over 60.
MD affects the macula 120, which is critical for acute vision, reading, and recognizing faces. MD can occur in people of any age, but usually affects older people. Because of lengthening average life-expectancy, MD has become increasingly common, and thus, the study and treatment of MD has become increasingly more important.
In a person with MD, the macula 120 begins to deteriorate in various ways. In particular, distorted central vision occurs in or near the center of the visual field. MD is associated with photoreceptor damage and a roughened macula 120, often caused by the presence of fluid or blood in the subretinal space. This roughening results in distortion of the patient's central field of vision. There are two types of MD, “dry MD” and “wet MD.” Symptoms usually develop gradually and painlessly, and vary depending on the form. Most cases of MD start as the dry type, which also is the most common type. In 15 percent of cases, the disease advances to the wet type, often causing rapid vision loss.
The current approach to treatment of both types of MD vary depending on the patient and the type of MD. Treatments typically include injectable drug therapy, photodynamic therapy, laser treatment, surgery, and vitamin and mineral supplements to slow the advance of the disease. Research is focused on slowing or stopping the progression of the disease.
Thus there is a need in the art for devices that can improve the vision of MD patients. It can also be seen, then, that there is a need in the art for methods, apparatuses, and devices to help those with MD regardless of the current state of a given patient's vision.